Matra Murena lacking power - any ideas please?

[macaroni]

Hi,
I got my Matra Murena 2.2 tuned at a RR the other day. Racepower Motorsport near Maidstone. I've been there before and the old boy, Jim, knows his carbs.

It has a Chrysler 2.2 engine, same as in the Talbot Tagora and has been retro-fitted with twin Dellorto DHLA45s, a Holbay cam and 4-1 manifold.

I'd jetted the carbs myself, so was fairly sure they weren't perfect and the initial power run gave 101bhp @ fly.

I know all the arguments about flywheel power figures, but prior to my car, the RR guy tested a short-oval-circuit Toyota Starlet with a standard 1.3 engine which gave 70bhp at the flywheel. which is exactly what they should produce. Thus, I was reasonably confident in the power figures.

Anyway, the air correctors were reduced in size slightly to get a nice 13:1 AFR at the top end. The ignition timing was spot on with a max advance of 35 degrees. On the rollers, at 6750 rpm, the car hit 137mph in top!
The final power figure was 105bhp, which is well low. These cars should make 118 as standard and 130 - 140 with the mods my car has. It is an old car (1982), but the engine has only done 65000 miles.
I did a compression check and all the cylinders made a consistent 150psi, which is a bit low, but not disastrous.

The car drives fine, albeit a bit thirsty, but doesn't have any real go that 130bhp in a 1000kg car should have.

So my question is what else should I check to try and regain the missing horsies?

I've checked the valve clearance, which were a bit tight, but now spot on.
The ignition system has been replaced, new dizzy cap, rotor arm, plugs, coil, ignition amp.
No air leaks as far as I can tell as the pop-up lights work fine off the engine vacuum.

I'm out of thoughts, anyone??

Cheers,

Antony

[demag]

It hasn't been standing has it? You know stale petrol and all that.

[macaroni]

Absolutely not, I use it every day on a 40 mile round motorway commute!

[AndersDK]

Would this be the all-alu J6TA500 engine also found in the '85-'90 CX22 models ?
(The Douvrin engine)
This engine is known as a real workhorse, only weakness being low tolerant to coolant problems, as this instantly makes the HG start leaking.

I'd say you have a bog standard valve timing or valve clearance problem, or the exhaust is partly blocked by debries.

Be sure to use an engne oil specified for this era of engine design : no thinner than 10W40 viscosity, or it may start showing blow-by problems eating up your hi-end Bhp's.

[macaroni]

Hi and thanks for the reply,
no it isn't the Douvrin engine, although many get confused and think it is.
Its a 2155cc engine developed from the Chrysler 180 and fitted to the Talbot Tagora. It has a cast iron block and alloy OHC head.
The transaxle is from a CX however.

The valve clearances are fine, but yes, it could be a timing problem. Thing is, the timing is not adjustable and there are no vernier pulleys available for this engine.
The only thing I thought of is that the timing chain could be one tooth out, is that possible?

[AndersDK]

I'm not familiar with that engine type.
But any engine could be set wrong on the valve timing, though I doubt it if it is an old style steelchain timing setup.
That would mean the valve timing was set 3-5deg wrong ever since the chain has been off from its last service job. Would certainly eat up the last important umph from the engine.

Must be some kind of indexing on both axles to line up for checking the timing ?

[jeremy]

Its also possible for timing chain wear to be a problem. The rough test is to try and stretch and compress the chain and see what slack there is. Sometimes its possible to lift a link where it passes over a gear.

Single row chains are more prone to the problem than double (or even triple) chains.

Obviously the design of the drive will be significant - and I'd have thought your OHC engine would have had quite a long chain.